1. Technical Field
The present invention relates to an electrical fuse and, more particularly, to an electrical fuse, a semiconductor device having the same, and a method of programming and reading the electrical fuse.
2. Discussion of the Related Art
Semiconductor memory devices (chips) disposed on a semiconductor substrate are electrically tested before an assembly process. As a result, the semiconductor chips are classified as either defective or good. When a malfunction occurs in at least one defective cell of the defective chips, the defective cell is replaced by a redundant cell in a repair process. In order to allow the redundant cell to use an address of the defective cell in write and read modes, predetermined fuses are blown (for example, programmed) using the repair process. It may be confirmed whether the fuses are blown or not by sensing the resistance with the application of a voltage to both ends of each of the fuses on which the repair process is performed.
The fuses may be a laser fuse, which is blown using laser, or an electrical fuse, which is blown by applying a voltage.
FIG. 1 is a plan view of a conventional electrical fuse.
Referring to FIG. 1, the electrical fuse is disposed on a semiconductor substrate 10. The electrical fuse includes a cathode 12 and an anode 14, which are spaced apart from each other, and a fuse link 16, which combines the cathode 12 with the anode 14. For example, the cathode 12 and the anode 14 are coupled in series by the fuse link 16. The cathode 12 has a larger area than the anode 14. Contact plugs 18 are disposed on the anode 14 to contact interconnections (not shown), and contact plugs 20 are disposed on the cathode 12 to contact interconnections (not shown).
A program voltage higher than a threshold voltage is applied to the cathode 12 and the anode 14 such that the electrical fuse is blown. Generally, a negative voltage is applied to the cathode 12, while a positive voltage is applied to the anode 14. Thus, electrical migration EM and thermal migrations TM1 and TM2 occur between the cathode 12 and the anode 14. Particularly, current crowding occurs at a boundary region A between the cathode 12 and the fuse link 16. The electrical migration occurs from the cathode 12 toward the anode 14.
FIG. 2 is a graph illustrating the distribution of thermal migration that occurs by the application of a program voltage to the conventional electrical fuse shown in FIG. 1.
Referring to FIGS. 1 and 2, when a program voltage is applied to the conventional electrical fuse, first thermal migration TM1 occurs from the center M/2 of the fuse link 16 toward the anode 14, while second thermal migration TM2 occurs from the center M/2 of the fuse link 16 toward the cathode 12. The first thermal migration TM1 occurs in the same direction as the electrical migration EM. However, the second thermal migration TM2 occurs in an opposite direction to the electrical migration EM. Thus, the second thermal migration TM2 prevents the electrical fuse from being programmed (or blown). As a result, the reliability of the repair process deteriorates.